Should I buy a 2005 Giant Faith 3?

So I'm 15, and just starting to get into downhilling. Soon, I'm going to buy my first good downhill bike. I know someone who is selling a 2005 Giant Faith 3, mostly stock stuff, but it's my first bike so I don't think I need a all custom expensive bike?

Well anyway he's asking 900. He only rode it a few times but didn't like downhilling. Should i get it? or look into a different bike?

Also, is it really heavy? like will I be able to ride it around town/in my bmx park some?